Our laboratory has found a previously unknown lipid in brain, the sulfogalactosyl diacylglycerol, and has studied its metabolism and its close relation to myelination. We shall use this sulfolipid, which also exists in an alkylacyl form, and the galactosyl diacylglycerols as molecular markers of myelin. Through these marker metabolites we hope to gain some insight into the regulation (hormonal and metabolic feed-back effectors) of myelination, and to study the transfer of myelin constituents from site of synthesis in digodedroglia to the myelin membrane. Both whole animal (normal and mutants), dissociated brain cell cultures, and pure transformed cell culture lines will be used. A primary culture system of dissociated brain cells from 15 day mice embryos has been developed and used successfully by our laboratory to show a direct stimulating effect on triiodothyromine on the synthesis of myelin-associated biochemical parameters.